Oral thrush: All you need to know

Oral thrush, also known as oral candidiasis, is a yeast/fungi infection of the genus Candida that develops on the mucous membranes of the mouth.

It is most commonly caused by the fungus Candida albicans, but may also be caused by Candida glabrata or Candida tropicalis.

For the majority of individuals, oral thrush does not cause any serious problems. However, this is not the case for people with a weakened immune system, whose signs and symptoms may be much more severe.

The outcome for oral thrush is generally very good. Most people respond well to treatment. However, oral thrush tends to reappear, especially if the causal factor (smoking, for instance) is not removed.

In this article, we will cover all aspects of oral thrush, including the causes, symptoms, and treatment.

Fast facts on oral thrush

Here are some key points about oral thrush. More detail and supporting information is in the main article.

Oral thrush is a common condition, but for most, it does not cause major problems.

Individuals with a reduced immune system are worst affected by oral thrush.

Hyperplastic – also referred to as “plaque-like candidiasis” or “nodular candidiasis” due to the presence of a hard to remove solid white plaque. This is the least common variant; it is most often seen in patients with HIV.

There are a number of other lesions that can also appear with oral thrush. Sometimes, these lesions might be due to other types of bacteria that are also present in the area. These can include:

Angular cheilitis – inflammation and/or splitting in the corners of the mouth

Median rhomboid glossitis – a large, red, painless mark in the center of the tongue

Linear gingival erythema – a band of inflammation running across the gums

Tiny quantities of Candida fungus exist in various parts of our body, including the digestive system, skin, and mouth, causing virtually no problems to healthy individuals. In fact, C. albicans is carried in the mouths of up to 75 percent of the world’s population.

However, people on certain medications, with reduced immune systems, or certain medical conditions are susceptible to oral thrush when C. albicans grows out control.

Adult oral thrush is more likely to become a problem for the following groups:

People who wear dentures – especially if they are not kept clean, do not fit properly, or are not taken out before going to sleep.

Antibiotics – people who are on antibiotics have a higher risk of developing oral thrush. Antibiotics may destroy the bacteria that prevent the Candida from growing out of control.

Excessive mouthwash use – individuals who overuse antibacterial mouthwashes may also destroy bacteria which keep Candida at bay, thus increasing the risk of developing oral thrush.

Steroid medication – long-term use of steroid medication can increase the risk of oral thrush.

Weakened immune system – people with weakened immune systems are more likely to develop oral thrush.

Diabetes – people with diabetes, especially if it is poorly controlled, are more likely to have oral thrush.

Dry mouth – people with less than normal quantities of saliva (xerostomia) are more prone to oral thrush.

Diet – malnutrition predisposes people to oral thrush; this could be caused by a poor diet or a disease that affects the absorption of nutrients. In particular, diets low in iron, vitamin B12, and folic acid appear to affect infection rates.

Smoking – heavy smokers are more at risk, the reasons behind this are unclear.